Laser irradiation apparatus with means for applying magnetic field

ABSTRACT

According to the present invention, oxygen and nitrogen are effectively prevented from mixing into the semiconductor film by doping Ar or the like in the semiconductor film in advance, and by irradiating the laser light in the atmosphere of Ar or the like. Therefore, the variation of the impurity concentration due to the fluctuation of the energy density can be suppressed and the variation of the mobility of the semiconductor film can be also suppressed. Moreover, in TFT formed with the semiconductor film, the variation of the on-current in addition to the mobility can be also suppressed. Furthermore, in the present invention, the first laser light converted into the harmonic easily absorbed in the semiconductor film is irradiated to melt the semiconductor film and to increase the absorption coefficient of the fundamental wave.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a continuous wave laser irradiationapparatus utilized for crystallizing a semiconductor film. In addition,the present invention relates to a method for manufacturing asemiconductor device including a process for crystallizing thesemiconductor film with the use of the laser irradiation apparatus.

2. Description of the Related Art

A thin film transistor using a polycrystalline semiconductor film(polycrystalline TFT) is superior to TFT using an amorphoussemiconductor film in its mobility by double digits or more and has anadvantage that a pixel portion and its peripheral driver circuit in asemiconductor display device can be integrally formed on the samesubstrate.

The polycrystalline semiconductor film can be formed over an inexpensiveglass substrate when a laser annealing method is employed. However, theenergy of the laser light output from the oscillator fluctuates by atleast a few percentage points due to the various reasons. Thisfluctuation prevents the semiconductor film from being crystallizedhomogeneously. When the crystallinity of the polycrystallinesemiconductor film varies due to the inhomogeneous crystallization, thecharacteristic of TFT using the polycrystalline semiconductor film asits active layer such as on-current or the mobility also varies.

For example, in the case of an active matrix light-emitting device witha light-emitting element and a TFT for controlling current supplied tothe light-emitting element provided in each pixel, when the on-currentof TFT varies, the luminance of the light-emitting element also variesaccordingly.

Moreover, when the semiconductor film is crystallized by the irradiationof the laser light in the atmosphere, the surface of the semiconductorfilm becomes somewhat rough. The higher the energy intensity of thelaser light is, the rougher the surface of this semiconductor filmbecomes. The light is scattered to give more brightness in the regionwhose surface is rougher. Therefore, sometimes the striped light andshade are visible at intervals of several mm due to the energyfluctuation.

It is noted that the state of the surface of the semiconductor film isclosely related to the oxygen in the atmosphere when the laser light isirradiated according to the patent application shown below.

Published patent application No. 2000-138180 (P.3-P.4) describes thatthe more oxygen the atmosphere contains, the rougher the surface of thesemiconductor film crystallized with the irradiation of the laser lightbecomes. The application also describes to spray the semiconductor filmwith Ar when the laser light is irradiated.

When the surface of the semiconductor film becomes rough, interfacestate density at the interface between the semiconductor film and a gateinsulating film formed so as to contact the semiconductor film becomeshigh and the threshold voltage shifts to normally-off side. Therefore,when the state of the surface of the semiconductor film becomes unevendue to the energy fluctuation of the laser light, the interface statedensity at the interface between the semiconductor film and the gateinsulating film formed afterward varies, which results in the variationof the threshold of TFT.

When the laser light having high absorption coefficient to thesemiconductor film is employed, it is possible to crystallize thesemiconductor film more effectively. The absorption coefficient dependson the material and the thickness of the semiconductor film. However,When a silicon film having a thickness from several tens nm to severalhundreds nm which is usually used in the semiconductor device iscrystallized by an excimer laser or a YVO₄ laser, the second harmonichaving a shorter wavelength than the fundamental wave is higher inabsorption coefficient and thereby it is possible to crystallize moreeffectively.

For this reason, in order to enhance the efficiency of thecrystallization, the wavelength is usually converted through anon-linear optical element. The laser light converted into the harmonic,however, tends to have lower energy compared with the case of thefundamental wave. For example in the case of Nd:YAG laser, theconversion efficiency from the fundamental wave (wavelength: 1064 nm) tothe second harmonic (wavelength: 532 nm) is approximately 50%. When theenergy of the laser light decreases, the throughput in thecrystallization also decreases, which results in the lowering of theproductivity.

Moreover, since the non-linear optical element is easy to deterioratedue to the laser light and is inferior in endurance, when the energy ofthe fundamental wave is increased in order to obtain the laser light ofthe harmonic having high energy, it is necessary to do the maintenancefrequently. Therefore, this is not preferable.

3. Problem Solved by the Invention

In view of the problem described above, it is an object of the presentinvention to provide a laser irradiation apparatus being able tosuppress the unevenness of the crystallinity or the state of the surfaceof the semiconductor film and to perform homogeneous crystallization ofthe semiconductor film. It is another object of the present invention toprovide a method for manufacturing a semiconductor device with the useof the laser irradiation apparatus being able to suppress the variationof the on-current, the mobility, and the threshold of TFT.

Furthermore, it is an object of the present invention to provide a laserirradiation method and a laser processing apparatus having highthroughput in view of the problem described above.

SUMMARY OF THE INVENTION

The energy density of the laser light is assumed to have a very closerelation with the crystallinity of the semiconductor film. However, thepresent inventors considered that such a wide variation of thecrystallinity as causing the visible variation of the luminance cannotbe explained only with the fluctuation of the energy density by a fewpercentage points. Therefore, the present inventors examined thesecondary factor caused by the fluctuation of the energy density thataffects the crystallinity.

The present inventors focused on a mixture of oxygen or nitrogenexisting in the atmosphere into the semiconductor film melted by thelaser light.

The semiconductor film melted instantaneously by the irradiation of thelaser light seems to be recrystallized at a comparatively rapid rate ofseveral tens m/s when irradiated with the pulsed laser light, andseveral cm/s when irradiated with the CW laser light. Therefore, it isassumed that the impurities exist in the air dissolve in thesemiconductor film more than the solubility in thermal equilibriumstate.

The irradiation time of the laser light for crystallizing thesemiconductor film also depends on the scanning speed, and in the caseof using the pulsed laser light, the irradiation time of the laser lightranges from several to several tens ns. On the other hand, in the caseof using the CW laser light, the irradiation time is comparatively longin the range from several to several tens μs. Therefore, the CW laserlight melts the semiconductor film longer than the pulsed laser light.For this reason, it is considered that the impurities in the air areeasier to be mixed into the semiconductor film in the case of using theCW laser light.

The higher the temperature of the semiconductor film is, the more easilythe impurities in the air dissolve in the semiconductor film, becausethe solubility of the gas increases. Therefore, it is assumed that whenthe heat given to the semiconductor film makes difference of elevationdue to the fluctuation of the energy density, the impurity concentrationin the semiconductor film varies.

Since the impurities such as oxygen or nitrogen mixed from theatmosphere are positive in segregation coefficient in the meltedsemiconductor film, they are easy to be segregated in the gain boundaryat the time of recrystallization. This phenomenon is called grainboundary segregation and is more likely to be seen in the impurity whosesolid solubility is lower. The segregated impurity such as oxygen ornitrogen is easy to combine with silicon to form the insulator such assilicon oxide, silicon nitride oxide, or silicon nitride. And theinsulator segregated in the grain boundary prevents the carrier frommoving in the semiconductor film and this causes the decreasing of themobility.

Therefore, it is considered that the variation of the impurityconcentration due to the fluctuation of the energy density causes thevariation of the mobility of the semiconductor film.

Consequently, the present inventors tried to enhance the crystallinityby performing the following processes. Ar is doped in the semiconductorfilm before crystallizing it with the irradiation of the laser light,and then the semiconductor film is irradiated with the laser light inthe atmosphere of Ar. It is noted that the element to be doped is notlimited to Ar and any other zeroth group elements (noble gas element)may be employed. Moreover, when the laser light is irradiated, Ar is notalways necessary in the atmosphere, and the gas of the zeroth groupelement or the gas of the zeroth group element added with hydrogen maybe employed. The zeroth group element is appropriate in point of thatthe zeroth group element does not become a dopant because it is neutralin the semiconductor film, and that the zeroth group element is hard toform the compound with the element constituting the semiconductortypified by silicon. Particularly, since Ar is inexpensive, the costrequired for manufacturing a semiconductor device can be reduced. It isnoted that not only an ion doping method but also an ion implantationmethod may be employed as means for adding the zeroth group element tothe semiconductor film.

The processes from doping Ar up to irradiating the laser light to thesemiconductor film are performed in the load lock system chamber inorder not to expose the semiconductor film in the atmosphere includingoxygen. For example, with the manufacturing apparatus of themulti-chamber system including a chamber to perform the process to forma semiconductor film, a chamber to perform the process to dope Ar to thesemiconductor film, and a chamber to irradiate the semiconductor filmwith the laser light, it is possible to perform a series of processes inorder without exposing the semiconductor film to the atmosphere.

The mass of the gas that can dissolve in a certain amount of liquid isin proportion to the partial pressure of the gas contacting the liquid.Therefore, when the semiconductor film is doped with Ar or the like inadvance and then it is irradiated with the laser light in the atmosphereof Ar or the like, it is possible to prevent oxygen and nitrogen frommixing into the semiconductor film from the atmosphere effectively.

Therefore, it is possible to suppress the variation of the impurityconcentration due to the fluctuation of the energy density, and tosuppress the variation of the mobility of the semiconductor film. In TFTformed by using the semiconductor film, it is also possible to suppressthe variation of the on-current in addition to the mobility.

As described in patent application No. 2000-138180, empirically, whenthe laser light is irradiated in the atmosphere including oxygen, thesurface of the semiconductor film becomes rough. With the composition ofthe present invention, however, it is possible to suppress the roughnessof the semiconductor surface due to the irradiation of the laser lightand to suppress the variation of the threshold caused by the variationof the interface state density.

In addition, when the semiconductor film melts, it is considered that aflow is generated in the semiconductor film due to the temperaturegradient or the difference of the surface tension. The present inventorsconsidered that the impurities such as oxygen or nitrogen mixed from thesurface of the semiconductor film are distributed in such a way that theimpurity is inclined locally due to the flow. The irregularity of theflow in the semiconductor film increases with the temperature of thesemiconductor film. As a result, since the impurities are dissolvedagain microscopically in recrystallization, the interface between thesolid phase and the liquid phase becomes inhomogeneous, and thereby theimpurities are inclined irregularly.

Consequently in the present invention, a magnetic field is applied tothe semiconductor film when the laser light is irradiated in order tosuppress the flow. Silicon is semiconductor in a solid phase. On theother hand, it is conductive material in a liquid phase. When themagnetic field is applied to the conductive material, the current isgenerated inside the conductor moving across the magnetic line of forceaccording to Fleming's law, and the conductive material receives a forcefrom a direction opposite to the moving direction by this current. As aresult, the viscosity increases to suppress the flow. Therefore, thesegregation of the impurities due to the flow can be suppressed and thevariation of the mobility and the on-current can be also suppressed.

In addition, it is also considered that when the viscosity of thesemiconductor film increases by applying the magnetic field, it ispossible to prevent the impurities from mixing into the semiconductorfilm and to increase the mobility of the semiconductor film more.

It is noted that the magnetic field may be applied by electromagneticinduction with a coil or the like, or may be applied by a permanentmagnet. As the permanent magnet, a neodymium magnet, a samarium-cobaltmagnet, an anisotropic ferrite magnet, an isotropic ferrite magnet, analnico magnet, a NdFeB bonded magnet, or the like can be used.

It is noted that in the present invention, the semiconductor film may beirradiated with the laser light after the catalyst element is addedthereto so as to enhance the crystallinity.

Moreover, in the present invention, a first laser light converted intothe harmonic, which is easy to be absorbed in the semiconductor film,and a second laser light having the fundamental wave are irradiatedsimultaneously to the semiconductor film in order to crystallize it.Specifically, the first laser light has a shorter wavelength than thevisible light.

In the present invention, the first laser light converted into theharmonic which is easy to be absorbed in the semiconductor film isirradiated to melt the semiconductor film and to increase the absorptioncoefficient of the fundamental wave. When the second laser light havinga wavelength of the fundamental wave is irradiated in such a state, thesemiconductor film in which the absorption coefficient of thefundamental wave is increased absorbs the second laser lighteffectively, and thereby it is possible to enhance the throughput of thelaser crystallization.

Since the wavelength of the second laser light does not need to beconverted, it is not necessary to suppress the energy in considerationof deterioration of the non-linear optical element. For example, thesecond laser light can have 100 times or more output than the firstlaser light. Therefore, it is no longer necessary to do the troublesomemaintenance of the non-linear optical element, which can enhance thetotal energy of the laser light absorbed in the semiconductor film and alarger crystal grain can be obtained.

It is noted that the number of laser light is not limited to two, andthe number thereof may be two or more. A plurality of the laser lighthaving a wavelength of the harmonic may be employed. In addition, aplurality of the second laser light having a wavelength of thefundamental wave may be also employed.

Furthermore, with the irradiation of the fundamental wave, it ispossible to provide advantageous effects that the sharp fall in thetemperature of the semiconductor film in the laser crystallization issuppressed and that the crystal grows so as to have a larger sized grainin addition to the advantageous effect that the energy of the harmonicis assisted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) to 1(C) shows the relation between the direction of themagnetic line of force and scanning direction of the beam spot and thesubstrate in the laser irradiation apparatus of the present invention.

FIGS. 2(A) and 2(B) shows the relation between the direction of themagnetic line of force and the scanning direction of the beam spot andthe substrate in the laser irradiation apparatus of the presentinvention.

FIGS. 3(A) and 3(B) shows the relation between the direction of themagnetic line of force and the scanning direction of the beam spot andthe substrate in the laser irradiation apparatus of the presentinvention.

FIGS. 4(A) and 4(B) shows the structure of the optical system in thelaser irradiation apparatus of the present invention.

FIG. 5 shows the structure of the optical system in the laserirradiation apparatus of the present invention.

FIGS. 6(A) to 6(C) shows the method for manufacturing a semiconductordevice.

FIGS. 7(A) to 7(D) shows the method for manufacturing a semiconductordevice.

FIGS. 8(A) to 8(D) shows the method for manufacturing a semiconductordevice.

FIG. 9 shows the structure of the laser irradiation apparatus having aload lock system chamber.

FIG. 10 is a cross-sectional view of the light-emitting devicemanufactured with the laser irradiation apparatus of the presentinvention.

FIGS. 11(A) to 11(D) shows the method for manufacturing a semiconductordevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment ModesEmbodiment Mode 1

A laser irradiation method of the present invention is explained withreference to FIG. 1. FIG. 1(A) shows an aspect in which a semiconductorfilm 101 formed over a substrate 100 is irradiated with laser light. Inthe present invention, the semiconductor film 101 is doped with thezeroth group element which is hard to form a compound with thesemiconductor and which is neutral in the semiconductor film so that itdoes not function as a dopant before the crystallization by theirradiation of the laser light.

He, Ne, Ar, Kr, Xe, or the like is given as the zeroth group element tobe doped. As well as the doping of P and B imparting conductivity to thesemiconductor film, the zeroth group element can be doped by convertingit into plasma and accelerating it with a porous electrode. Unlike P andB restricted legally, the gas to be doped does not have to be dilutedwith hydrogen and thereby the throughput is high.

For example, in the case of Ar, Ar is doped so that the concentration inthe semiconductor film ranges from 1×10¹⁸ atoms/cm³ to 1×10²¹ atoms/cm³,preferably from 5×10¹⁸ atoms/cm³ to 5×10²⁰ atoms/cm³. The acceleratingvoltage affects the concentration distribution of Ar in a direction ofthe thickness of the semiconductor film 101. Therefore, the accelerationvoltage is determined appropriately by the condition in which theconcentration is made higher toward the surface side of the film, theconcentration is made higher toward the substrate side of the film, orthe concentration is made uniform all over the film.

In addition, the semiconductor film 101 is irradiated with the laserlight in the atmosphere of the zeroth group element described above. Itis noted that the zeroth group element doped in the semiconductor filmand the zeroth group element used when the laser light is irradiated donot always have to be the same.

It is noted that the laser light may be irradiated in the atmosphere ofthe gas of the zeroth group element added with hydrogen. In this case,the partial pressure of hydrogen is set in the range of 1 to 3%.

In FIG. 1(A), a reference numeral 102 a denotes the first beam spotobtained by the first laser light having a wavelength of the harmonicirradiated to the semiconductor film 101. A reference numeral 102 bdenotes the second beam spot obtained by the second laser light having awavelength of the fundamental wave irradiated to the semiconductor film101.

The first laser light or the second laser light is emitted from acontinuous wave gas laser, solid laser, or metal laser. As the gaslaser, an Ar laser, a Kr laser, a XeF excimer laser, a CO₂ laser, andthe like are given. As the solid laser, a YAG laser, a YVO₄ laser, a YLFlaser, a YAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser,a Ti:Sapphire laser, and the like are given. As the metal laser, ahelium—cadmium laser, a copper vapor laser, a gold vapor laser, and thelike are given.

The wavelength of the first laser light is converted into the secondharmonic to the fourth harmonic through the non-linear optical element.Since the wavelength of the harmonic depends on the kind of the laserfor use, the harmonic is selected appropriately according to the laser.For example, in the case of Nd:YVO₄ laser (wavelength: 1064 nm), it isdesirable to employ the second harmonic (532 nm) or the third harmonic(355 nm). Specifically, the laser light emitted from the CW YVO₄ laseris converted into the harmonic with an output of 10 W through thenon-linear optical element.

It is noted that the non-linear optical element may be provided insidethe resonator included in the oscillator or the resonator equipped withthe non-linear optical element may be provided separately aside from theresonator of the fundamental wave. The former structure has an advantagethat the apparatus can be made small and thereby the accurate control ofthe resonator length is not necessary any more. On the other hand, thelatter structure has an advantage that the interaction of thefundamental wave and the harmonic can be ignored.

As the non-linear optical element, the crystal whose non-linear opticalconstant is relatively large such as KTP (KTiOPO₄), BBO (β-BaB₂O₄), LBO(LiB₃O₅), CLBO (CsLiB₆O₁₀), GdYCOB (YCa₄O(BO₃)₃), KDP (KD₂PO₄), KB5,LiNbO₃, Ba₂NaNb₅O₁₅ or the like is used. Especially, the crystal such asLBO, CLBO, or the like can enhance conversion efficiency from thefundamental wave into the harmonic.

It is desirable that the first laser light and the second laser lightare TEM₀₀ mode (single mode) obtained from the stable resonator. In thecase of TEM₀₀ mode, the beam spot is easily processed because the laserlight has Gaussian intensity distribution and it is superior in lightconverging.

The positions of the first beam spot 102 a and the second beam spot 102b are controlled so as to overlap each other. Therefore, the part of thesemiconductor film 101 irradiated with the beam spot 102 a is melted bythe first laser light and the absorption coefficient increases. For thisreason, the second laser light is absorbed in the semiconductor filmeffectively in the part overlapped with the first beam spot 102 a andthe second beam spot 102 b. Thus the throughput can be enhanced in theprocess of crystallization.

It is noted that the first laser light and the second laser light do notalways have to be emitted from the same laser. For example, the firstlaser light may be emitted from the Nd:YVO₄ laser generating the secondharmonic having an output of 10 W, and the second laser light may beemitted from the YAG laser having an output of 30 W. Of course, thepresent invention is not limited to this combination.

When the substrate 101 is scanned to the direction indicated by an arrowof a continuous line, the relative positions of the first beam spot 102a and the second beam spot 102 b to the semiconductor film 101 move.

A reference numeral 103 denotes a magnetic pole of a magnetic circuitbeing able to apply a magnetic field to the semiconductor film 101,particularly to the part thereof overlapped with the first beam spot 102a and the second beam spot 102 b. A magnetic line of force of themagnetic field generated from the magnetic pole 103 is shown with anarrow of a dotted line.

In order to clarify the relation between the direction of the magneticline of force and the scanning direction of the substrate to thesemiconductor film 101, FIG. 1(B) shows a top view of the semiconductorfilm 101, and FIG. 1(C) shows a cross-sectional view taken along adotted line A-A′ in FIG. 1(B). In FIG. 1, the scanning direction of thesubstrate 100 exists in the surface of the substrate 100 as shown withan arrow of a continuous line. The relative positions of the first beamspot 102 a and the second beam spot 102 b to the semiconductor film 101move to the direction indicated by the white arrow by the scanning ofthe substrate 100.

The magnetic pole 103 is provided in the side of the substrate 100opposite to the side thereof irradiated with the laser light. And themagnetic line of force is directed to the surface of the semiconductorfilm 101 from the magnetic pole 103.

It is noted that the surface formed with the semiconductor film 101 isnot always perpendicular to the direction of the magnetic line of force.In the present invention, it does not lead to any problems as long asthe magnetic component in which the direction of passing magnetic lineof force is almost constant is applied in the part of the semiconductorfilm 101 overlapped with the first beam spot 102 a and the second beamspot 102 b.

And the magnetic flux density in the part of the semiconductor film 101overlapped with the first beam spot 102 a and the second beam spot 102 bis set in the range of 1000 G to 10000 G, preferably in the range of1500 G to 4000 G.

FIG. 1 shows a case in which a surface formed with the semiconductorfilm 101 is perpendicular to the direction of the magnetic line of forcein the part of the semiconductor film 101 overlapped with the first beamspot 102 a and the second beam spot 102 b. In this case, the scanningdirection of the substrate 100 and the direction of the magnetic line offorce are also perpendicular. The direction of the magnetic line offorce, however, is not limited to that shown in the FIG. 1.

It is noted that in order to prevent the total energy of the laser lightabsorbed in the semiconductor film from being different in the partoverlapped with the first beam spot 102 a and the second beam spot 102 band in the part not overlapped, it is the most preferable that the firstbeam spot 102 a is overlapped with the second beam spot 102 bcompletely. In order to raise the proportion of the region havinghomogeneous energy density in the first beam spot 102 a, it is desirablethat the first beam spot 102 a has a linear shape, a rectangular shape,or an elliptical shape in which a ratio of the length of the major axisto that of the minor axis is five or more.

In this embodiment mode, as shown in the FIG. 1(B), Wb, which is thelength of the first beam spot 102 a in the direction of its major axis,is made shorter than W_(m1), which is the width of the magnetic pole 103in the direction of the major axis of the first beam spot 102 a, so thatthe direction of passing magnetic line of force can be kept almostconstant in the part of the semiconductor film 101 irradiated with thefirst beam spot 102 a, more preferably in the part overlapped with thefirst beam spot 102 a and the second beam spot 102 b.

In the present invention, as described above, oxygen or nitrogen can beprevented from mixing into the semiconductor film effectively by dopingAr or the like in the semiconductor film in advance and by irradiatingthe laser light in the atmosphere of Ar or the like. Therefore, thevariation of the impurity concentration due to the fluctuation of theenergy density can be suppressed. Moreover, the variation of themobility of the semiconductor film can be suppressed. And in TFT formedusing the semiconductor film, the variation of the on-current inaddition to the mobility can be suppressed.

As described in patent application No. 2000-138180, empirically, whenthe laser light is irradiated in the atmosphere including oxygen, thesurface of the semiconductor film becomes rough. However, when the laserlight is irradiated in the atmosphere of Ar or the like, such roughnesscan be suppressed, and the variation of the threshold due to thevariation of the interface state density can be suppressed.

Furthermore, when the magnetic field is applied to the semiconductorfilm at the time of laser irradiation, the segregation of the impuritiesdue to the flow can be suppressed. By further applying the magneticfield, the viscosity of the semiconductor film can be increased, andthereby the impurities are prevented from mixing into the semiconductorfilm. As a result, it is possible to suppress the variation of themobility and the on-current.

In addition, in the present invention, the semiconductor film is meltedwith the irradiation of the first laser light converted into theharmonic that is easy to be absorbed in the semiconductor film and theabsorption coefficient of the fundamental wave is increased. When thesecond laser light having the fundamental wave is irradiated in such astate, the second laser light can be absorbed effectively in thesemiconductor film in which the absorption coefficient of thefundamental wave is increased. Therefore, the throughput of the lasercrystallization can be enhanced.

Embodiment Mode 2

This embodiment mode explains one mode of the present invention in whichthe magnetic field is applied to the different direction from that inthe case of FIG. 1.

FIG. 2(A) is a top view of a semiconductor film 201 and FIG. 2(B) is across-sectional view taken along a dotted line A-A′ in FIG. 2(A). It isnoted that a reference numeral 201 denotes the semiconductor film formedover a substrate 200 in FIG. 2(A) and FIG. 2(B).

The scanning direction of the substrate 200 exists in the surface of thesubstrate 200 as indicated by an arrow of a continuous line. Inaddition, a reference numeral 202 a denotes the first beam spot obtainedby the first laser light having a wavelength of the harmonic irradiatedto the semiconductor film 202. A reference numeral 202 b denotes thesecond beam spot obtained by the second laser light having a wavelengthof the fundamental wave irradiated to the semiconductor film 202.

The first laser light and the second laser light are emitted from the CWgas laser, solid laser, or metal laser. The lasers cited in theembodiment mode 1 can be employed, for example.

The wavelength of the first laser light is converted from thefundamental wave to the second harmonic, the third harmonic, or thefourth harmonic through the non-linear optical element. Since thewavelength of the harmonic depends on the kind of the laser, theappropriate harmonic is selected according to the laser to be used. Thecrystals cited in the embodiment mode 1 can be used as the non-linearoptical element, for example.

It is desirable that the first laser light and the second laser lightare TEM₀₀ mode (single mode) obtained from the stable resonator. In thecase of TEM₀₀ mode, the beam spot is easily processed because the laserlight has Gaussian intensity distribution and it is superior in thelight converging.

The positions of the first beam spot 202 a and the second beam spot 202b are controlled so as to overlap each other. Therefore, the part of thesemiconductor film 201 irradiated with the first beam spot 202 a ismelted by the first laser light and the absorption coefficientincreases. For this reason, the second laser light is absorbed in thesemiconductor film 201 effectively in the part overlapped with the firstbeam spot 202 a and the second beam spot 202 b. Thus, the throughput inthe process of the crystallization can be enhanced.

When the substrate 200 is scanned to the direction indicated by an arrowof a continuous line, the relative positions of the first beam spot 202a and the second beam spot 202 b to the semiconductor film 201 move tothe direction indicated by a white arrow.

Magnetic poles 203 a and 203 b correspond to the magnetic poles of themagnetic circuit being able to apply the magnetic field to thesemiconductor film 201, particularly to the part overlapped with thefirst beam spot 202 a and the second beam spot 202 b. The magnetic lineof force of the magnetic field generated between the magnetic poles 203a and 203 b is shown with an arrow of a dotted line. The magnetic poles203 a and 203 b are provided in both sides of the substrate 200irradiated with the laser light, and the direction of the magnetic lineof force exists in the surface of the semiconductor film 201. In FIG. 2,the scanning direction of the substrate 200 is perpendicular to thedirection of the magnetic line of force in the part of the semiconductorfilm 201 overlapped with the first beam spot 202 a and the second beamspot 202 b.

It is noted that the magnetic line of force is distributed as connectingthe magnetic poles 203 a and 203 b. The magnetic line of force is almoststraight in the space where the distance from the magnetic poles 203 aand 203 b is shorter, but is curved to have a larger curvature as thedistance is longer. Therefore, the scanning direction of the substrate200 and the direction of the magnetic line of force are not alwaysperpendicular. In the present invention, it does not lead to anyproblems as long as the magnetic component in which the direction ofpassing magnetic line of force is almost constant is applied in the partof the semiconductor film 201 overlapped with the first beam spot 202 aand the second beam spot 202 b.

The magnetic flux density in the part of the semiconductor film 201overlapped with the first beam spot 202 a and the second beam spot 202 bis set in the range of 1000 G to 10000 G, preferably in the range of1500 G to 4000 G.

It is noted that in order to prevent the total energy of the laser lightabsorbed in the semiconductor film from being different in the partoverlapped with the first beam spot 202 a and the second beam spot 202 band in the part not overlapped, it is the most preferable that the firstbeam spot 202 a is overlapped with the second beam spot 202 bcompletely. In order to raise the proportion of the region havinghomogeneous energy density in the first beam spot 202 a, it is desirablethat the first beam spot 202 a has a linear shape, a rectangular shape,or an elliptical shape in which a ratio of the length of the major axisto that of the minor axis is five or more.

In this embodiment mode, as shown in the FIG. 2(A), Wb, which is thelength of the first beam spot 202 a in the direction of its major axis,is made shorter than W_(m2), which is the distance between the magneticpoles 203 a and 203 b, so that the direction of passing magnetic line offorce can be kept almost constant in the part of the semiconductor film201 irradiated by the first beam spot 202 a, more preferably in the partoverlapped with the first beam spot 202 a and the second beam spot 202b.

The amount of the applied magnetic field can be adjusted with the widthof Wm₂. Wm₂ is preferably in the range of 1 mm to 5 mm.

Embodiment Mode 3

This embodiment mode explains one mode of the present invention in whichthe magnetic field is applied to the direction different from those inthe case of FIG. 1 and FIG. 2.

FIG. 3(A) is a top view of a semiconductor film 301 and FIG. 3(B) is across-sectional view taken along a dotted line A-A′ in FIG. 3(A). It isnoted that a reference numeral 301 denotes the semiconductor film formedover a substrate 300 in FIGS. 3(A) and 3(B).

The scanning direction of the substrate 300 exists in the surface of thesubstrate 300 as indicated by an arrow of a continuous line. Inaddition, a reference numeral 302 a denotes the first beam spot obtainedby the first laser light having a wavelength of the harmonic irradiatedto the semiconductor film 302. A reference numeral 302 b denotes thesecond beam spot obtained by the second laser light having a wavelengthof the fundamental wave irradiated to the semiconductor film 302.

The first laser light and the second laser light are emitted from the CWgas laser, solid laser, or metal laser. The lasers cited in theembodiment mode 1 can be employed, for example.

The wavelength of the first laser light is converted from thefundamental wave to the second harmonic, the third harmonic, or thefourth harmonic through the non-linear optical element. Since thewavelength of the harmonic depends on the kind of the laser, theappropriate harmonic is selected according to the laser to be used. Thecrystals cited in the embodiment mode 1 can be used as the non-linearoptical element, for example.

It is desirable that the first laser light and the second laser lightare TEM₀₀ mode (single mode) obtained from the stable resonator. In thecase of TEM₀₀ mode, the beam spot is easily processed because the laserlight has Gaussian intensity distribution and is superior in the lightconverging.

The positions of the first beam spot 302 a and the second beam spot 302b are controlled so as to overlap each other. Therefore, the part of thesemiconductor film 301 irradiated with the first beam spot 302 a ismelted by the first laser light and the absorption coefficientincreases. For this reason, the second laser light is absorbed in thesemiconductor film 301 effectively in the part overlapped with the firstbeam spot 302 a and the second beam spot 302 b. Thus the throughput inthe process of the crystallization can be enhanced.

When the substrate 300 is scanned to the direction indicated by an arrowof a continuous line, the relative positions of the first beam spot 302a and the second beam spot 302 b to the semiconductor film 301 move tothe direction indicated by a white arrow.

Magnetic poles 303 a and 303 b correspond to the magnetic poles of themagnetic circuit being able to apply the magnetic field to thesemiconductor film 301, particularly to the part overlapped with thefirst beam spot 302 a and the second beam spot 302 b. The magnetic lineof force of the magnetic field generated between the magnetic poles 303a and 303 b is shown with an arrow of a dotted line. The magnetic poles303 a and 303 b are provided in both sides of the substrate 300irradiated with the laser light, and the direction of the magnetic lineof force exists in the surface of the semiconductor film 301. In FIG. 3,the scanning direction of the substrate 300 is parallel to and oppositeto the direction of the magnetic line of force in the part of thesemiconductor film 301 overlapped with the first beam spot 302 a and thesecond beam spot 302 b.

It is noted that the magnetic line of force is distributed as connectingthe magnetic poles 303 a and 303 b. The magnetic line of force is almoststraight in the space where the distance from the magnetic poles 303 aand 303 b is shorter, but is curved to have a larger curvature as thedistance is longer. Therefore, the scanning direction of the substrate300 and the direction of the magnetic line of force are not alwaysparallel. In the present invention, it does not lead to any problems aslong as the magnetic component in which the direction of passingmagnetic line of force is almost constant is applied in the part of thesemiconductor film 301 overlapped with the first beam spot 302 a and thesecond beam spot 302 b.

The magnetic flux density in the part of the semiconductor film 301overlapped with the first beam spot 302 a and the second beam spot 302 bis set in the range of 1000 G to 10000 G, preferably in the range of1500 G to 4000 G.

It is noted that in order to prevent the total energy of the laser lightabsorbed in the semiconductor film from being different in the partoverlapped with the first beam spot 302 a and the second beam spot 302 band in the part not overlapped, it is the most preferable that the firstbeam spot 302 a is overlapped with the second beam spot 302 bcompletely. In order to raise the proportion of the region havinghomogeneous energy density in the first beam spot 302 a, it is desirablethat the first beam spot 302 a has a linear shape, a rectangular shape,or an elliptical shape in which a ratio of the length of the major axisto that of the minor axis is five or more.

In this embodiment mode, as shown in the FIG. 3(A), Wb, which is thelength of the first beam spot 302 a in the direction of its major axis,is made shorter than W_(m3), which is the distance between the magneticpoles 303 a and 303 b, so that the direction of passing magnetic line offorce can be kept almost constant in the part of the semiconductor film301 irradiated with the first beam spot 302 a, more preferably in thepart overlapped with the first beam spot 302 a and the second beam spot302 b.

The amount of the applied magnetic field can be adjusted with the widthof Wm₃. Wm₃ is preferably in the range of 1 mm to 5 mm.

It is noted that as the method for scanning laser light, there are anirradiation system moving type method in which a substrate, a processedobject, is fixed while an irradiation position of laser light is moved,an processed object moving type method in which an irradiation positionof the laser light is fixed while a substrate is moved, and a method inwhich these two methods are combined.

In the embodiment modes 1 to 3, the case in which the laser irradiationapparatus with the processed object moving type method was explained,but the present invention is not limited to this. The present inventioncan be applied to the laser irradiation apparatus with the irradiationsystem moving type and to the laser irradiation apparatus in which anprocessed object moving type and an irradiation system moving type arecombined. In any case, it is premised that the relation between themoving direction of the beam spot relative to the semiconductor film andthe direction of the magnetic line of force can be controlled.

In addition, although the embodiment modes 1 to 3 employ the magneticfield generated between the heterogeneous magnetic poles attracting eachother, the present invention is not limited to this. The magnetic fieldgenerated between the homogeneous magnetic poles repelling each othermay be also employed. For example, when the homogeneous magnetic polesare employed as the magnetic poles 203 a and 203 b in FIG. 2, themagnetic field can be applied in the direction perpendicular to thesemiconductor film 201.

It is noted that the direction of the magnetic line of force is notlimited to those shown in the embodiment modes 1 to 3. The directionthereof may be opposite to those shown in the embodiment modes 1 to 3,and the magnetic line of force may be directed to have an angle so as tobe neither perpendicular nor parallel to the scanning direction of thelaser light and to the semiconductor film.

Embodiment Mode 4

This embodiment mode explains a structure of the optical system includedin the laser irradiation apparatus of the present invention.

FIG. 4(A) shows an example of the optical system for performing thelaser crystallization with the use of the first laser light having awavelength of the harmonic and the second laser light having awavelength of the fundamental wave. A reference numeral 701 denotes alaser oscillator oscillating the first laser light. The CW Nd:YVO₄ laserhaving the second harmonic (wavelength 532 nm) with an output of 10 W isused in FIG. 4(A). Although the second harmonic is used in FIG. 4(A),the present invention is not limited to this, and the other higherharmonics can be employed. However, the higher the harmonic is, thelower the conversion efficiency becomes. In addition, when thewavelength is too short, the laser light transmits through thesemiconductor film having a thickness in nanometers to micrometers,which results in the lowering of the crystallization efficiency.Therefore, it is preferable to employ the second harmonic.

A reference numeral 702 denotes a laser oscillator oscillating thesecond laser light. The CW Nd:YAG laser having the fundamental wave(wavelength 1.064 μm) with an output of 30 W is used in FIG. 4(A). Thefirst and the second laser light obtained from the laser oscillators 701and 702 are preferably TEM₀₀ mode (single mode).

After the first laser light oscillated from the laser oscillator 701 isreflected on a mirror 703, it is converged through a planoconvex lens704. And then the first laser light is irradiated to a semiconductorfilm 705 formed over a substrate. A reference numeral 706 denotes thefirst beam spot fainted on the semiconductor film 705 by the irradiationof the first laser light.

It is noted that an incidence angle θ1 of the first laser light to thesemiconductor film 705 is set to 20° in this embodiment mode. Theincidence angle θ1 is not limited to this, and it can be changedappropriately. The planoconvex lens 704 has a focal length of 20 mm, andthe plane portion thereof is kept parallel to the surface of thesemiconductor film 705. Moreover, the distance between the semiconductorfilm 705 and the planoconvex lens 704 is set to approximately 20 mm.This forms the first beam spot 706 having a size of approximately 500 μmin its major axis and approximately 20 μm in its minor axis and having ashape similar to ellipse.

On the other hand, the second laser light oscillated from the laseroscillator 702 is converged through a planoconvex lens 707 and then isirradiated to the semiconductor film 705 formed over the substrate. Areference numeral 708 denotes the second beam spot formed on thesemiconductor film 705 by the irradiation of the second laser light.

The incidence angle θ₂ of the second laser light to the semiconductorfilm 705 is set to 40° in this embodiment mode. The incidence angle θ₂is not limited to this, and it can be changed appropriately. Theplanoconvex lens 707 has a focal length of 15 mm, and the plane portionthereof is kept parallel to the surface of the semiconductor film 705.This forms the second beam spot 708 having a size of approximately 1 mmin its major axis and approximately 0.2 mm in its minor axis and havinga shape similar to ellipse.

The first beam spot 706 and the second beam spot 708 are completelyoverlapped. A stage 709 can move to XY directions on the surfaceparallel to the surface of the semiconductor film 705 using a uniaxialrobot for X-axis 710 and a uniaxial robot for Y-axis 711. It isappropriate that the scanning rate ranges from several tens cm/s toseveral hundreds cm/s and it is set to 50 cm/s here.

Next, another example of the optical system included in the laserirradiation apparatus of the present invention is explained.

In FIG. 4(B), laser light output from four laser oscillators arecombined to form the first laser light to be used. In FIG. 4(B), four ofthe CW Nd:YVO₄ lasers each of which has an output of 10 W and has awavelength of the second harmonic (532 nm) are used to form the firstlaser light. It is noted that although the second harmonic is used inthis embodiment mode, the present invention is not limited to this andthe other higher harmonics can be used.

Four of the first laser light being incident from the directionindicated by an arrow are incident into four cylindrical lenses 719 to722 respectively. The two laser light shaped through the cylindricallenses 719 and 721 make again the form of the beam spots through thecylindrical lens 717 and then the formed beam spots are irradiated tothe substrate 723 with the semiconductor film formed thereover. On theother hand, the two laser light shaped through the cylindrical lenses720 and 722 make again the form of the beam spots through thecylindrical lens 718, and then the formed beam spots are irradiated tothe substrate 723.

It is possible for a designer to determine the focal length of each lensand the incidence angle appropriately. However, the focal length of thecylindrical lenses 717 and 718, which are positioned closest to thesubstrate 723, is made shorter than those of the cylindrical lenses 719to 722. For example, the focal lengths of the cylindrical lenses 717 and718, which are positioned closest to the substrate 723, are set to 20mm. And the focal lengths of the cylindrical lenses 719 to 722 are setto 150 mm. Each lens is arranged so that the incidence angle of thelaser light from the cylindrical lenses 717 and 718 to the processedobject 700 is 25° and the incidence angle of the laser light from thecylindrical lenses 719 to 722 to the cylindrical lenses 717 and 718 is10°.

Each of the beam spots of the first laser light on the substrate 723overlaps partially one another to be combined so as to form the firstbeam spot. The first beam spot is shaped into the elliptical having asize of approximately 400 μm in its major axis and approximately 20 μmin its minor axis.

The second laser light can be obtained from the laser oscillator with anoutput of 500 W. The CW Nd:YAG laser having a wavelength of thefundamental wave (1.064 μm) is used as the laser oscillator. The firstand the second laser light obtained from the laser oscillators 701 and702 are preferably TEM₀₀ mode (single mode).

The second laser light is converged through a planoconvex lens 725 andis irradiated to the semiconductor film formed over the substrate 723.It is noted that instead of the planoconvex lens 725, two cylindricallenses may be employed in such a way that they are orthogonalized.

The semiconductor film is crystallized by overlapping the first beamspot obtained by four of the first laser light with the second beam spotobtained by the second laser light. The first beam spot and the secondbeam spot are completely overlapped. In FIG. 4(B), the lasercrystallization is performed in such a way that, for example, thesubstrate is moved using a uniaxial robot for X-axis and a uniaxialrobot for Y-axis as shown in FIG. 4(A). It is appropriate that thescanning rate is in the range of several tens cm/s to several hundredscm/s and it is set to 50 cm/s here.

Next, another example of the optical system included in the laserirradiation apparatus of the present invention is explained.

In FIG. 5, a reference numeral 731 denotes a laser oscillatoroscillating the first laser light. The CW Nd:YVO₄ laser having awavelength of the second harmonic (532 nm) with an output of 10 W isused as the laser oscillator 731. It is noted that although the secondharmonic is used in FIG. 5, the present invention is not limited tothis, and the other higher harmonics may be also employed.

A reference numeral 732 denotes a laser oscillator oscillating thesecond laser light. The CW Nd:YAG laser having a wavelength of thefundamental wave (1.064 μm) with an output of 2000 W is used as thelaser oscillator. The first and the second laser light obtained from thelaser oscillators 731 and 732 are preferably TEM₀₀ mode (single mode).

The first laser light oscillated from the laser oscillator 731 isconverged to be elliptical through the beam expander including twocylindrical lenses 733 and 734. The converged laser light is reflectedby a galvanometer minor 735, and then it is converged again through anfθ lens (F-θ lens) 736. After that it is irradiated to a semiconductorfilm 737 formed over the substrate. A reference numeral 738 denotes thefirst beam spot formed on the semiconductor film 737 by the irradiationof the first laser light. The first beam spot 738 is the ellipticalhaving a size of 20 μm in its minor axis and 400 μm in its major axis,for example.

The first beam spot 738 can be scanned by changing the angle of thegalvanometer mirror 735. The fθ lens 736 can prevent the beam spot fromchanging in shape due to the change of the angle of the galvanometermirror as much as possible. The incident angle of the first laser lightto the semiconductor film 737 is set to 20°. The laser light can beirradiated to the whole surface of the semiconductor film 737 when thegalvanometer mirror 735 is combined with the uniaxial stage in thisembodiment mode. The first laser light is scanned preferably at a speedranging from 100 to 2000 mm/s, preferably about 500 mm/s.

On the other hand, after the second laser light oscillated from thelaser oscillator 732 is expanded uniformly through a concave lens 741,the second laser light is converged in one direction through aplanoconvex cylindrical lens 739 and then it is irradiated to thesemiconductor film 737 formed over the substrate. A reference numeral740 denotes the second beam spot formed on the semiconductor film 737 bythe irradiation of the second laser light. In this embodiment mode, thesecond beam spot 740 is scanned to one direction by covering the wholeregion scanned by the first beam spot 738 with the second beam spot 740so that it can be easily synchronized with the first beam spot 738. Itis also possible to use a beam homogenizer in order to form the secondbeam spot 740 being able to cover the whole region scanned by the firstbeam spot 738.

It is desirable that an incidence angle θ of the laser light satisfiesthe inequality of θ≧arctan (W/2d). In the inequality, it is defined thatan incidence plane is perpendicular to the surface to be irradiated andis including a longer side or a shorter side of the beam spot assumingthat the beam spot is rectangular in shape. Moreover, in the inequality,“W” is the length of the longer side or the shorter side included in theincidence plane and “d” is the thickness of the substrate havingtransparency to the laser light, which is placed at the surface to beirradiated. It is defined that a track of the laser light projected tothe incidence plane has an incidence angle θ when the track is not onthe incidence plane. When the laser light is made incident at anincidence angle θ, it is possible to perform uniform irradiation of thelaser light without interference of reflected light from a surface ofthe substrate with reflected light from a rear surface of the substrate.The theory above is considered assuming that a refractive index of thesubstrate is 1. In fact, the substrate has a refractive index ofapproximately 1.5, and a larger value than the angle calculated inaccordance with the above theory is obtained when the value around 1.5is taken into account. However, since the beam spot has energyattenuated at opposite sides in the longitudinal direction thereof, theinterference has a small influence on opposite sides and the valuecalculated in accordance with the inequality is enough to obtain theeffect of attenuating the interference. The inequality with respect to θis applicable only to the substrate transparent to the laser light.

It is noted that the optical system included in the laser irradiationapparatus of the present invention is not limited to that shown in thisembodiment mode.

Embodiment Mode 5

This embodiment mode explains specifically the method for crystallizingthe semiconductor film with the laser irradiation apparatus of thepresent invention.

Initially, as shown in FIG. 6(A), a base film 501 is formed over asubstrate 500. As the substrate 500, a glass substrate such as a bariumborosilicate glass and an alumino—borosilicate glass, a quartzsubstrate, an SUS substrate, or the like can be used. Moreover, althougha substrate made from flexible synthetic resin such as plastic usuallytends to be inferior in heat resistance to the substrate 500 describedabove, it can be used as long as it resists the heat generated in themanufacturing process.

The base film 501 is provided so that alkaline metal such as Na oralkaline-earth metal included in the substrate 500 may not diffuse intothe semiconductor film to have an adverse affect on a characteristic ofa semiconductor element. Therefore, the base film 501 is formed of aninsulating film such as silicon oxide, silicon nitride, or siliconnitride oxide, which can suppress the diffusion of the alkaline metal orthe alkaline-earth metal into the semiconductor film. In this embodimentmode, a silicon nitride oxide film is formed in thickness from 10 nm to400 nm (preferably from 50 nm to 300 nm) by the plasma-CVD method.

It is noted that the base film 501 may be formed in single layer or inlaminated layer of a plurality of insulating films. In the case to usethe substrate including the alkaline metal or the alkaline-earth metalin any way such as the glass substrate, the SUS substrate, or theplastic substrate, it is effective to provide the base film in order toprevent the diffusion of the impurities. On the other hand, when thediffusion of impurities does not lead to any significant problems, thebase film does not always have to be provided.

Next, a semiconductor film 502 is formed over the base film. Thethickness of the semiconductor film 502 is set in the range of 25 nm to100 nm (preferably in the range of 30 nm to 60 nm). It is noted that thesemiconductor film 502 may be amorphous semiconductor orpoly-crystalline semiconductor. Moreover, not only silicon but alsosilicon germanium can be used as the semiconductor. When silicongermanium is used, it is preferable that the concentration of germaniumranges from 0.01 atomic % to 4.5 atomic %.

Next, the zeroth group element is added to the semiconductor film 502 byan ion dope method (ion doping method). This embodiment mode explains anexample in which Ar is used as the zeroth group element (currentlyreferred to as the 18th element). For example, in the case of Ar, Ar isadded so that the concentration in the semiconductor film ranges from1×1018 atoms/cm3 to 1×1021 atoms/cm3, preferably from 5×1018 atoms/cm3to 5×1020 atoms/cm3. And the accelerating voltage affects theconcentration distribution of Ar in the direction of the thickness ofthe semiconductor film 502. Therefore, the acceleration voltage isdetermined appropriately by the condition in which the concentration ismade higher toward the surface side of the film, the concentration ismade higher toward the substrate side of the film, or the concentrationis made uniform all over the film. In this embodiment mode, theaccelerating voltage was set to 30 kV.

It is noted that the laser light may be irradiated in the atmosphere ofthe gas with hydrogen added to the zeroth group element. In this case,the partial pressure of hydrogen is set in the range of 1% to 3%.

Next, as shown in FIG. 6(B), the semiconductor film 502 is crystallizedwith the laser irradiation apparatus of the present invention. In thisembodiment mode, the Nd:YVO4 laser outputting the second harmonic (532nm) having an energy of 5.5 W was used as the first laser light. As thesecond laser light, the Nd:YAG laser outputting the fundamental wave(1.064 μm) having an energy of 15 W was used.

And in the present invention, the magnetic field is applied withmagnetic poles 504 and 505 to the region irradiated with the laserlight. In this embodiment mode, the scanning direction of the laserlight and the direction of the magnetic line of force in the magneticfield are corresponded. In FIG. 6(B), the relative moving direction ofthe laser light to the substrate 500 is shown with a white arrow whilethe direction of the magnetic line of force is shown with an arrow of adotted line.

It is noted that the magnetic line of force is distributed as connectingthe magnetic poles 504 and 505. The magnetic line of force is almoststraight in the space where the distance from the magnetic poles 504 and505 is shorter, but is curved to have a larger curvature as the distanceis longer. Therefore, the moving direction of the beam spot is notalways parallel to the direction of the magnetic line of force. In thepresent invention, it does not lead to any problems as long as themagnetic component in which the direction of passing magnetic line offorce is almost constant is applied in the part 506 of the semiconductorfilm 502 irradiated with the beam spot.

The magnetic flux density in the part 506 irradiated with the beam spotis in the range of 1000 G to 10000 G, preferably in the range of 1500 Gto 4000 G.

The laser light is irradiated in the atmosphere including the gas of thezeroth group element for 99.99% or more, preferably 99.9999% or more, inthe load lock system chamber. In this embodiment mode, Ar is used as thezeroth group element.

It is noted that the zeroth group element that is doped and the zerothgroup element that is used when the laser light is irradiated does notalways have to be the same.

The semiconductor film 503 having further enhanced crystallinity isformed by irradiating the laser light to the semiconductor film 502 asdescribed above.

Next, as shown in FIG. 6(C), the semiconductor film 503 is patterned toform island-shaped semiconductor films 507 to 509 and various kinds ofsemiconductor elements, typically TFT, are formed with theseisland-shaped semiconductor films 507 to 509.

When TFT is manufactured, for example, a gate insulating film is formedso as to cover the island-shaped semiconductor films 507 to 509. As thegate insulating film, silicon oxide, silicon nitride, silicon nitrideoxide, or the like can be used. The plasma-CVD method, the sputteringmethod, or the like can be employed as the film-forming method.

Next, a gate electrode is formed by forming and patterning a conductivefilm on the gate insulating film. And the gate electrode or resist beingformed and patterned is used as a mask, and the impurities impartingn-type or p-type conductivity is added to the island-shapedsemiconductor films 507 to 509 to form a source region, a drain region,an LDD region, and the like.

TFT can be formed through such a series of processes. It is noted thatthe method for manufacturing the semiconductor device in the presentinvention is not limited to the process for manufacturing TFT describedabove following after forming the island-shaped semiconductor films. Thevariations of the on-current, the threshold, and the mobility betweenthe elements can be suppressed when the semiconductor film crystallizedwith the laser irradiation method of the present invention is employedas an active layer of TFT.

Embodiment Mode 6

Unlike the embodiment mode 5, this embodiment mode explains an examplein which the crystallization method by the laser irradiation apparatusof the present invention is combined with a crystallization method bythe catalyst element.

Initially, the processes from forming the semiconductor film 502 up todoping the semiconductor film 502 with the zeroth group element areperformed in reference up to FIG. 6(A) in the embodiment mode 5. Next,the surface of the semiconductor film 502 is coated with nickel acetatesolution including Ni in the range of 1 ppm to 100 ppm in weight by aspin coating method. It is noted that the catalyst may be added not onlyby the spin coating method but also by the sputtering method, the vapordeposition method, the plasma process, or the like.

Next, a heating process was performed for 4 hours to 24 hours at atemperature ranging from 500° to 650°, for example for 14 hours at atemperature of 570°. This heating process forms the semiconductor film520 in which the crystallization is promoted in the vertical directiontoward the substrate 500 from the surface coated with nickel acetatesolution. (FIG. 7(A))

It is noted that although nickel (Ni) is used as the catalyst element inthis embodiment mode, the other element such as germanium (Ge), Iron(Fe), Palladium (Pd), Tin (Sn), Lead (Pb), Cobalt (Co), Platinum (Pt),Copper (Cu), or Gold (Au) may be also used.

Next, as shown in FIG. 7(B), the semiconductor film 520 is crystallizedusing the laser irradiation apparatus of the present invention. In thisembodiment mode, the Nd:YVO₄ laser outputting the second harmonic (532nm) having an energy of 10 W was used as the first laser light. As thesecond laser light, the Nd:YAG laser outputting the fundamental wave(1.064 μm) having an energy of 500 W was used.

And in the present invention, the magnetic field is applied to theregion irradiated with the laser light with a magnetic pole 527 from theside of the substrate 500 opposite to the side of the substrate 500 withthe semiconductor film 520 formed thereover. In this embodiment mode,both the scanning direction of the laser light and the surface formedwith the semiconductor film 520 are made perpendicular to the directionof the magnetic line of force in the magnetic field. In FIG. 7(B), therelative moving direction of the laser light to the substrate 500 isdrawn with a white arrow, while the direction of the magnetic line offorce is drawn with an arrow of a dotted line.

It is noted that the surface formed with the semiconductor film 520 isnot necessarily perpendicular to the direction of the magnetic line offorce. In the present invention, it does not lead to any problems aslong as the magnetic component where the direction of passing magneticline of force is almost constant is applied in the part 528 of thesemiconductor film 520 irradiated with a beam spot.

And the magnetic flux density in the part 528 irradiated with the beamspot is set in the range of 1000 G to 10000 G, preferably in the rangeof 1500 G to 4000 G.

The laser light is irradiated in the atmosphere including the zerothgroup element gas for 99.99% or more, preferably 99.9999% or more, inthe load lock system chamber. In this embodiment mode, Ar is used as thezeroth group element.

It is noted that the zeroth group element that is doped and the zerothgroup element that is used when the laser light is irradiated does notalways have to be the same.

The semiconductor film 521 whose crystallinity is further enhanced isformed by irradiating the laser light to the semiconductor film 520 asdescribed above.

It is considered that the catalyst element (Ni here) is included at aconcentration of approximately 1×10¹⁹ atoms/cm³ in the semiconductorfilm 521 that is crystallized with the catalyst element as shown in FIG.7(B). Next, the catalyst element existing in the semiconductor film 521is gettered.

First, an oxide film 522 is foliated over the surface of thesemiconductor film 521 as shown in FIG. 7(C). By forming the oxide film522 having a thickness from 1 nm to 10 nm, the surface of thesemiconductor film 521 can be prevented from becoming rough due to theetching in the following etching process.

The oxide film 522 can be formed by a known method. For example, theoxide film 522 may be formed by oxidizing the surface of thesemiconductor film 521 using ozone water or using the solution in whichhydrogen peroxide solution is mixed with sulfuric acid, hydrochloricacid, nitric acid, or the like. Alternatively, the oxide film 522 may beformed by the plasma process, heating process, or ultraviolet rayirradiation in the atmosphere including oxygen. Moreover, the oxide filmmay be formed separately by the plasma-CVD method, the sputteringmethod, the vapor deposition method, or the like.

A semiconductor film 523 for the gettering including the noble gaselement not less than 1×10²⁰ atoms/cm³ is formed in thickness from 25 nmto 250 nm over the oxide film 522 by the sputtering method. It isdesirable that the mass density of the semiconductor film 523 for thegettering is lower than that of the semiconductor film 521 in order toincrease the selecting ratio of the etching to the semiconductor film521.

As the noble gas element, one kind or plural kinds selected from thegroup consisting of Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr),and Xenon (Xe) are used.

Next the gettering is performed through the heating process by thefurnace annealing method or the RTA method. When the furnace annealingmethod is employed, the heating process is performed for 0.5 hours to 12hours at a temperature ranging from 450° to 600° in the atmosphere ofnitrogen. When the RTA method is employed, a lamp light source forheating is turned on for 1 to 60 seconds, preferably 30 seconds to 60seconds, which is repeated from 1 time to 10 times, preferably from 2times to 6 times. The lamp light source may have any luminescenceintensity, but the luminescence intensity is set so that thesemiconductor film is heated instantaneously at a temperature rangingfrom 600° to 1000°, preferably from 700° to 750°.

Through the heating process, the catalyst element inside thesemiconductor film 521 moves to the semiconductor film 523 for thegettering due to the diffusion as indicated by an arrow and the catalystelement is thus gettered.

Next, the semiconductor film 523 for the gettering is removed by etchingselectively. The etching process is performed by dry etching with ClF₃not applying plasma, or by wet etching with alkali solution such as thesolution including hydrazine or tetraethylammonium hydroxide((CH₃)₄NOH). On this occasion, the oxide film 522 prevents the oxidefilm 521 from being etched.

Next, the oxide film 522 is removed by hydrofluoric acid.

Next, the semiconductor film 521 after removing the oxide film 522 ispatterned to form the island-shaped semiconductor films 524 to 526 (FIG.7(D)).

It is noted that the gettering process in the present invention is notlimited to the method described in this embodiment mode. The catalystelement in the semiconductor film may be reduced with the other method.

Next, various semiconductor elements, typified by TFT, are formed usingthese island-shaped semiconductor films 524 to 526.

It is noted that the crystallinity of the semiconductor film can be moreenhanced compared with the case in the embodiment mode 5 when thesemiconductor film is crystallized with the irradiation of the laserlight after it is crystallized with the catalyst element as described inthis embodiment mode. In the embodiment mode 5, the crystallization ispromoted in such a way that crystal nuclei arise randomly after beingirradiated with the laser light. On the other hand, in this embodimentmode, the crystal formed in the crystallization by the catalyst elementstays as it is without being melted by the irradiation of the laserlight in the side closer to the substrate and the crystallization ispromoted by having the crystal as its crystal nuclei. As a result, thecrystallization by the irradiation of the laser light is easy to bepromoted from the substrate side to the surface uniformly, and thus thesurface is prevented from becoming rough compared with the case of theembodiment mode 5. Therefore, the variation of the characteristic of thesemiconductor element, typically TFT, can be more suppressed.

It is noted that this embodiment mode explained the process to promotecrystallization by performing the heating process after the catalystelement is added, and then to enhance crystallinity further byirradiating the laser light. However, the present invention is notlimited to this, and the heating process may be omitted. Specifically,after adding the catalyst element, the laser light may be irradiatedinstead of the heating process in order to enhance the crystallinity.

Embodiment Mode 7

This embodiment mode, unlike the embodiment mode 6, explains an examplein which the crystallizing method using the laser irradiation apparatusof the present invention is combined with the crystallizing method usingthe catalyst element.

Initially, the processes from forming the semiconductor film 502 todoping the zeroth group element to the semiconductor film 502 areperformed in reference up to FIG. 6(A) in the embodiment mode 5. Next, amask 540 having an opening was formed over the semiconductor film 502.And the nickel acetate solution including Ni in the range of 1 ppm to100 ppm in weight was applied to the surface of the semiconductor film502 by the spin coating method. It is noted that the method for addingthe catalyst element is not limited to this, and the sputtering method,the vapor deposition method, the plasma process, or the like may be alsoemployed. Applied nickel acetate solution contacts the semiconductorfilm 502 in the opening of the mask 540. (FIG. 8(A))

Next, the heating process was performed for 4 hours to 24 hours at atemperature ranging from 500° to 650°, for example for 14 hours at atemperature of 570°. This heating process forms a semiconductor film 530in which the crystallization is promoted from the surface coated withthe nickel acetate solution as indicated by an arrow of a continuousline. (FIG. 8(A))

It is noted that the catalyst element cited in the embodiment mode 6 canbe used as the catalyst element.

Next, after the mask 540 is removed, the semiconductor film 530 iscrystallized using the laser irradiation apparatus of the presentinvention as shown in FIG. 8(B). In this embodiment mode, the Nd:YVO₄laser outputting the second harmonic (532 nm) having an energy of 10 Wwas used as the first laser light. As the second laser light, the Nd:YAGlaser outputting the fundamental wave (1.064 μm) having an energy of2000 W was used.

And in the present invention, the magnetic field is applied with the useof magnetic poles 541 and 542 to the region irradiated by the laserlight. In this embodiment mode, the scanning direction of the laserlight and the direction of the magnetic line of force are corresponded.In FIG. 8(B), the relative moving direction of the laser light to thesubstrate 500 is shown with a white arrow while the direction of themagnetic line of force is shown with an arrow of a dotted line.

It is noted that the magnetic line of force is distributed as connectingthe magnetic poles 541 and 542. The magnetic line of force is almoststraight in the space where the distance from the magnetic poles 541 and542 is shorter, but is curved to have a larger curvature as the distanceis longer. Therefore, the moving direction of the beam spot is notalways parallel to the direction of the magnetic line of force. In thepresent invention, it does not lead to any problems as long as themagnetic component in which the direction of passing magnetic line offorce is almost constant is applied in the part 538 of the semiconductorfilm 530 irradiated with the beam spot.

The magnetic flux density in the region 538 irradiated with the beamspot is set in the range of 1000 G to 10000 G, preferably in the rangeof 1500 G to 4000 G.

The laser light is irradiated in the atmosphere including the zerothgroup element gas for 99.99% or more, preferably 99.9999% or more, inthe load lock system chamber. In this embodiment mode, Ar is used as thezeroth group element gas.

It is noted that the zeroth group element that is doped and the zerothgroup element that is used when the laser light is irradiated does notalways have to be the same.

A semiconductor film 531 having further enhanced crystallinity is formedby irradiating the laser light to the semiconductor film 530 asdescribed above.

It is noted that as shown in FIG. 8(B), the semiconductor film 531crystallized with the catalyst element is assumed to include thecatalyst element (Ni here) at a concentration of approximately 1×10¹⁹atoms/cm³. Sequentially the catalyst element existing in thesemiconductor film 531 is gettered.

As shown in FIG. 8(D), a silicon oxide film 532 for a mask is formed 150nm in thickness so as to cover the semiconductor film 530. And then anopening is provided by patterning the semiconductor film 530 to expose apart of the semiconductor film 530. Then, phosphorous is added toprovide a region 533 in which phosphorous is added in the semiconductorfilm 530.

When the heating process is performed in this state for 5 hours to 24hours at a temperature ranging from 550° to 800° in the atmosphere ofnitrogen, for example for 12 hours at a temperature of 600°, the region533 added with phosphorous in the semiconductor film 530 works as agettering site. As a result, the catalyst element left in thesemiconductor film 530 is segregated in the gettering region 533 withphosphorous added therein. (FIG. 8(B))

And the concentration of the catalyst element in the rest of the regionsin the semiconductor film 530 can be decreased to 1×1017 atms[sic]/cm3or less by removing the region 533 added with phosphorous by means ofetching.

After removing the silicon oxide film 532 for the mask, thesemiconductor film 531 is patterned to form island-shaped semiconductorfilms 534 to 536. (FIG. 8(D))

It is noted that the gettering process in the present invention is notlimited to the method shown in this embodiment mode. The other methodmay be employed in order to decrease the catalyst element in thesemiconductor film.

Next, as shown in FIG. 8(D), the semiconductor film 531 is patterned toform the island-shaped semiconductor films 534 to 536, which areutilized to form the various kinds of semiconductor elements typified byTFT.

It is noted that the crystallinity of the semiconductor film can be moreenhanced compared with the case of the embodiment mode 5 when thesemiconductor film is crystallized with the irradiation of the laserlight after it is crystallized with the catalyst element as described inthis embodiment mode. In the embodiment mode 5, the crystallization ispromoted in such a way that crystal nuclei arise randomly after beingirradiated with the laser light. On the other hand, in this embodimentmode, the crystal formed in the crystallization by the catalyst elementstays as it is without being melted by the irradiation of the laserlight in the side closer to the substrate and the crystallization ispromoted by having the crystal as its crystal nuclei. As a result, thecrystallization by the irradiation of the laser light is easy to bepromoted from the substrate side to the surface uniformly, and thus thesurface is prevented from becoming rough compared with the case in theembodiment mode 5. Therefore, the variation of the characteristic of thesemiconductor element, typically TFT, can be more suppressed.

It is noted that this embodiment mode explained the composition topromote the crystallization by performing the heating process after thecatalyst element is added, and then to enhance crystallinity further bythe irradiation of the laser light. However, the present invention isnot limited to this and the heating process may be omitted.Specifically, after adding the catalyst element, the laser light may beirradiated instead of the heating process in order to enhance thecrystallinity.

Embodiment Mode 8

This embodiment mode explains the structure of the laser irradiationapparatus including the load lock system chamber.

FIG. 9 shows the structure of the laser irradiation apparatus in thisembodiment mode. A laser irradiation chamber 1206 is surrounded by abarrier diffusion 1230. It is noted that since the laser light is highlydirectional and has the high energy density, the barrier diffusion 1230preferably has the characteristic of absorbing the reflected light inorder to prevent the reflected light from irradiating to aninappropriate region. In addition, cooling water may be circulated inthe barrier diffusion in order to prevent the rise of the temperaturedue to the absorption of the reflected light.

Moreover, as shown in FIG. 9, means 1240 for heating the barrierdiffusion (barrier diffusion heating means) may be provided to heat thebarrier diffusion when the laser irradiation chamber is evacuated.

And a gate 1210 corresponds to a transferring gate for transferring thesubstrate to the laser irradiation chamber 1206. The gas inside thelaser irradiation chamber 1206 can be evacuated by an evacuation system1231 connected to an evacuation port 1211. The noble gas can be suppliedinto the laser irradiation chamber 1206 by a noble gas supplying system1250 connected to a supply port 1251.

A reference numeral 1212 denotes a stage on which the substrate 1203 ismounted. When the stage is moved according to position controlling means1242, the position of the substrate can be controlled and theirradiation position of the laser light can be moved. As shown in FIG.9, means 1241 for heating the substrate (substrate heating means) may beprovided in the stage 1212.

An opening 1232 provided in the barrier diffusion 1230 is covered by awindow 1233 to transmit the laser light (transmission window). It ispreferable that the transmission window is made of the material that ishard to absorb the laser light. For example the quarts or the like isappropriate. A gasket 1236 is provided between the transmission window1233 and the barrier diffusion 1230. The gasket 1236 can prevent theatmosphere from entering the laser irradiation chamber from theinterspace between the transmission window 1233 and the barrierdiffusion 1230.

Initially, the substrate 1203 with the semiconductor film formed thereonis transferred. After the gate 1210 is closed, the laser irradiationchamber 1206 is kept with the atmosphere of the noble gas by using theevacuation system 1231 and the noble gas supplying system 1250.

The beam spot of the first laser light oscillated from a laseroscillator 1213 a is shaped through an optical system 1214 a and thesubstrate 1203 is irradiated with the shaped beam spot. In addition, thebeam spot of the second laser light oscillated from a laser oscillator1213 b is shaped through an optical system 1214 b and the substrate 1203is irradiated with the shaped beam spot. The incidence angle θ ispreferably set to more than 0°, more preferably between 5° and 30°, inorder to prevent the return light and to perform the uniformirradiation.

A reference numeral 1252 denotes the magnetic pole of the magneticcircuit, which applies the magnetic field to the semiconductor filmformed over the substrate 1203. It is noted that although the magneticfield is applied from the side of the substrate 1203 irradiated with thelaser light, the present invention is not limited to this. The magneticfield may be applied from the side of the substrate 1203 opposite to theside thereof irradiated with the laser light by incorporating themagnetic pole 1252 into the stage 1212.

It is noted that the laser irradiation chamber 1206 shown in FIG. 9 maybe one chamber included in the multi-chambers. When the chamber fordoping the noble gas element to the semiconductor film is provided sothat a series of the processes from doping the noble gas element up tocrystallizing with the laser light are performed in the multi-chamberwithout exposing it to the air, it is possible to prevent the impuritiesfrom mixing into the semiconductor film more effectively.

It is noted that when the laser irradiation apparatus is employed forcrystallizing the semiconductor film, it is possible to make thecrystallinity of the semiconductor film more uniform. The method formanufacturing the semiconductor device in the present invention can beapplied to manufacture the integrated circuit and the semiconductordisplay device. Particularly, when the present invention is applied tothe semiconductor element such as the transistor provided in the pixelportion of the semiconductor display device such as the liquid crystaldisplay device, the light-emitting device having the light-emittingelement typified by the organic light-emitting element equipped in eachpixel, DMD (Digital Micromirror Device), PDP (Plasma Display Panel), orFED (Field Emission Display), it is possible to prevent the horizontalstripes from being visible due to the energy distribution of the laserlight irradiated to the pixel portion thereof.

EMBODIMENTS

Hereinafter the embodiment of the present invention is explained.

Embodiment 1

A structure of the pixel in the light-emitting device, one of thesemiconductor devices formed using the laser irradiation apparatus ofthe present invention, is explained with reference to FIG. 10.

In FIG. 10, a base film 6001 is formed over a substrate 6000 and atransistor 6002 is formed over the base film 6001. The transistor 6002has an active layer 6003, a gate electrode 6005, and a gate insulatingfilm 6004 sandwiched between the active layer 6003 and the gateelectrode 6005.

A polycrystalline semiconductor film crystallized using the laserirradiation apparatus of the present invention is used as the activelayer 6003. It is noted that not only silicon but also silicon germaniummay be employed as the active layer. When the silicon germanium isemployed, it is preferable that the concentration of germanium is in therange of 0.01 atomic % to 4.5 atomic %. Alternatively silicon withcarbon nitride added may be also employed.

Silicon oxide, silicon nitride, or silicon oxynitride can be employed asthe gate insulating film 6004. Alternatively, a film in which these arelaminated, for example a film in which SiN is laminated on SiO₂ may beemployed as the gate insulating film. The SiO₂ film was formed with theplasma-CVD method mixing TEOS (Tetraethyl Orthosilicate) and O₂, at areaction pressure of 40 Pa, with a substrate temperature ranging from300° to 400°, by discharging at a high frequency (13.56 MHz) with anelectric density ranging from 0.5 W/cm² to 0.8 W/cm². Thus manufacturedsilicon oxide film obtains good characteristic as the gate insulatingfilm by performing the thermal annealing at a temperature ranging from400° to 500° thereafter. Aluminum nitride can be used as the gateinsulating film. The aluminum nitride is comparatively high in heatconductivity, and thereby the heat generated in TFT can be diffusedeffectively. Moreover, a film in which the aluminum nitride is laminatedon the silicon oxide, silicon oxynitride, or the like not includingaluminum may be used as the gate insulating film. Furthermore, SiO₂formed with RF sputtering method using Si as a target may be employed asthe gate insulating film.

The gate electrode 6005 is formed of the element selected from the groupconsisting of Ta, W, Ti, Mo, Al, and Cu, or is formed of a compoundmaterial or of an alloy material including the above element as its maincomponent. Alternatively a semiconductor film, typically apolycrystalline silicon film doped with the impurities such asphosphorous, may be employed. In addition, the gate electrode 6005 maybe formed of not only the conductive film of a single layer, but alsothe conductive films with a plurality of layers laminated.

For example, it is preferable that these conductive films have astructure in which the first conductive film is formed of a tantalumnitride (TaN) and the second conductive film is formed of W, a structurein which the first conductive film is formed of a tantalum nitride (TaN)and the second conductive film is formed of Ti, a structure in which thefirst conductive film is formed of tantalum nitride (TaN) and the secondconductive film is formed of Al, or a structure in which the firstconductive film is formed of tantalum nitride (TaN) and the secondconductive film is formed of Cu. Moreover, the semiconductor film,typically the polycrystalline silicon film doped with the impuritiessuch as phosphorous, or AgPdCu alloy may be employed as the first andthe second conductive films.

The conductive film may be formed not only in two-layers structure, butalso in three-layers structure in which for example a tungsten film, analloy film of aluminum and silicon (Al—Si), and a titanium nitride filmare laminated in order. When the conductive film is formed inthree-layers structure, tungsten nitride may be employed instead of thetungsten, an alloy film of aluminum and titanium (Al—Ti) may be employedinstead of the alloy film of aluminum and silicon (Al—Si), and atitanium film may be employed instead of the titanium nitride film. Itis important to select the optimum etching method and the optimum kindof etchant appropriately according to the material of the conductivefilm.

The transistor 6004 is covered with a first interlayer insulating film6006 on which a second interlayer insulating film 6007 and a thirdinterlayer insulating film 6008 are laminated. The first interlayerinsulating film 6006 can be formed of a silicon oxide film, a siliconnitride film, or a silicon oxynitride film in single layer or inlaminated layer with the plasma-CVD method or the sputtering method. Thefirst interlayer insulating film 6006 may be also formed of a film inwhich the silicon oxynitride film including more oxygen than nitrogen inmole fraction is formed on the silicon nitride oxide film including morenitrogen than oxygen in mole fraction. When the heating process (heatingprocess at a temperature ranging from 300° to 550° for 1 hour to 12hours) is performed after forming the first interlayer insulating film6006, it is possible to terminate (hydrogenation) the dangling bond ofthe semiconductor included in the active layer 6003 by hydrogen includedin the first interlayer insulating film 6006.

The second interlayer insulating film 6007 may be formed of an organicresin film, an inorganic insulating film, an insulating film includingSi—CH_(x) bond and Si—O bond made as the starting material from thesiloxane-based material or the like. In this embodiment,non-photosensitive acrylic is used. The third interlayer insulating film6008 is formed of a film which is harder to transmit the materialcausing to promote deterioration of the light-emitting element such asmoisture, oxygen, and the like compared with the other insulating films.It is preferable to use typically a DLC film, a carbon nitride film, asilicon nitride film formed with the RF sputtering method, or the like.

In FIG. 10, a reference numeral 6010 denotes an anode, a referencenumeral 6011 denotes an electroluminescent layer, a reference numeral6012 denotes a cathode, and the part in which the anode 6010, theelectroluminescent layer 6011, and the cathode 6012 are overlappedcorresponds to a light-emitting element 6013. One of the transistors6002 is a driver transistor for controlling the current supplied to thelight-emitting element 6013 and thereby it is connected directly orserially through the other circuit elements to the light-emittingelement 6013.

The electroluminescent layer 6011 has a structure of a singlelight-emitting layer or has a structure with a plurality of layersincluding the light-emitting layer laminated.

The anode 6010 is formed on the third interlayer insulating film 6008.An organic resin film 6014 is formed as the barrier diffusion on thethird interlayer insulating film 6008. The organic resin film 6014 hasan opening 6015 and the light-emitting element 6013 is formed byoverlapping the anode 6010, the electroluminescent layer 6011, and thecathode 6012 in the opening.

And a passivation film 6016 is formed on the organic resin film 6014 andthe cathode 6012. As well as the third interlayer insulating film 6008,the passivation film 6016 is formed of the film which is harder totransmit the material causing to promote deterioration of thelight-emitting element such as moisture and oxygen, for example a DLCfilm, a carbon nitride film, a silicon nitride film formed by the RFsputtering method, or the like. It is also possible to form thepassivation film by laminating the film that is hard to transmitmoisture, oxygen, and the like described above and a film which iseasier to transmit moisture, oxygen, and the like compared with theabove film.

In addition, the organic resin film 6014 is heated in the vacuumatmosphere in order to remove the moisture, oxygen, and the like stuckthereto before the electroluminescent layer 6011 is formed.Specifically, the heating process is performed in the vacuum atmosphereat a temperature ranging from 100° to 200° for 0.5 hours to 1 hour. Itis desirable that the pressure is set to 3×10⁻⁷ Torr or less, and it isthe most desirable that the pressure is set to 3×10⁻⁸ Torr or less ifpossible. When the electroluminescent layer is formed after the heatingprocess is performed to the organic resin film in the vacuum atmosphere,it is possible to enhance reliability by keeping it in the vacuumatmosphere until just before forming the electroluminescent layer.

In addition, it is desirable that the end of the opening 6015 in theorganic resin film 6014 is made into a round shape so that the endportion of the electroluminescent element layer 6011 formed so as topartially overlap on the organic resin film 6014 does not have a hole.To be more specific, it is desirable that the radius of curvature of thecurve line drawn by the sectional surface of the organic resin film inthe opening is in the range of 0.2 μm to 2 μm.

With the above structure, the coverage of the electroluminescent layerand the cathode that are formed later can be enhanced, and thereby it ispossible to prevent the anode 6010 and the cathode 6012 from shortingout in the hole formed in the electroluminescent layer 6011. Moreover,by relaxing the stress of the electroluminescent layer 6011, the defectin which the light-emitting region decreases, what is called shrink, canbe reduced to enhance the reliability.

In addition, FIG. 10 shows an example in which a positive photosensitiveacrylic resin is used as the organic resin film 6014. The photosensitiveorganic resin is classified into the positive type in which the regionexposed with the energy line such as beam, electron, ion, or the like isremoved, and the negative type in which the exposed region is notremoved. In the present invention, the organic resin film of thenegative type may be also used. Moreover, the organic resin film 6014may be formed of the photosensitive polyimide. When the organic resinfilm 6014 is formed of the acrylic of the negative type, the end sectionin the opening 6015 becomes an S character-like cross-sectional shape.On this occasion, it is desirable that the radius of the curvature inthe upper end and the lower end of the opening is in the range of 0.2 μmto 2 μm.

The anode 6010 can be formed of the transparent conductive film. Notonly ITO, but also the transparent conductive film in which indium oxideis mixed with tin oxide (ZnO) by 2% to 20% may be used. In FIG. 10, ITOis used as the anode 6010. The anode 6010 may be polished by CMP methodor by cleaning (bellcleaning) with porous body of polyvinyl alcohols sothat the surface of the anode 6010 is made flat. Furthermore, thesurface of the anode 6010 may be irradiated with the ultraviolet ray ormay be processed with oxygen plasma after polishing it with the CMPmethod.

The cathode 6012 can be formed of the other known material when it isthe conductive film having low work function. For example, Ca, Al, CaF,MgAg, AlLi, or the like is desirable.

It is noted that FIG. 10 shows the structure in which the light emittedfrom the light-emitting element is irradiated to the side of thesubstrate 6000. However, the structure in which the light is irradiatedto the side opposite to the substrate may be also employed.

In addition, although the transistor 6002 is connected to the anode 6010of the light-emitting element in FIG. 10, the present invention is notlimited to this structure, and the transistor 6002 may be connected tothe cathode 6012 of the light-emitting element. In this case, thecathode is formed on the third interlayer insulating film 6008 using TiNor the like.

In fact, after the state shown in FIG. 10 is obtained, it is preferableto pack (enclose) with the passivation film (laminated film, ultravioletcured resin film, or the like) or transparent cover member, which ishighly airtight and hardly degassing in order not to be exposed to air.The reliability of OLED is enhanced when the inside of the cover memberis filled with the inert atmosphere or the material havingmoisture-absorption characteristic (barium oxide, for example) is set inthe cover member.

It is noted that the light-emitting device of the present invention isnot limited to the manufacturing process described above. Moreover, thesemiconductor device in the present invention is not limited to thelight-emitting device.

Embodiment 2

This embodiment explains a shape of the first beam spot obtained bycombining a plurality of the first laser light shown in FIG. 4(B). It isnoted that the first beam spot is referred to as a beam spot simply inthis embodiment.

FIG. 11(A) shows an example of the shape of the beam spot of the laserlight oscillated from each of a plurality of laser oscillators on aprocessed object. The beam spot shown in FIG. 11(A) is elliptical inshape. It is noted that the shape of the beam spot of the laser lightoscillated from the laser oscillator is not limited to elliptical in thepresent invention. The shape of the beam spot depends on the kind of thelaser, and the shape thereof can be changed through an optical system.For example, the laser light emitted from the excimer laser L3308manufactured by Lambda Physik, Inc. (wavelength 308 nm, pulse with 30ns) is rectangular in shape having a size of 10 mm×30 mm (both are widthat half maximum in a beam profile). On the other hand, the laser lightemitted from a YAG laser having a cylindrical rod is circular in shape.The laser light emitted from a YAG laser having a slab rod isrectangular in shape. These laser light can be also changed into thelaser light having a desired size by further shaping them through theoptical system.

FIG. 11(B) shows energy density distribution of the laser light in Ydirection of a major axis of the beam spot shown in FIG. 11(A). The beamspot shown in FIG. 11(A) corresponds to the region satisfying the energydensity that is 1/e² of the peak value of the energy density in FIG.11(B). The energy density distribution of the laser light whose beamspot is elliptical becomes higher toward the center O of the ellipse.

Next, FIG. 11(C) shows the shape of the beam spots when the laser lighthaving the beam spot shown in FIG. 11(A) is combined. It is noted thatFIG. 11(C) shows the case in which four beam spots of the laser lightare overlapped to form one linear beam spot but the number of theoverlapped beam spots is not limited to this.

As shown in FIG. 11(C), the beam spots of the laser light are combinedto form one beam spot in such a way that the major axis of each ellipseis corresponded and the beam spots are overlapped partially one another.It is noted that the straight line obtained by connecting the center Oof each ellipse is defined as the center axis of the beam spot.

FIG. 11(D) shows the energy density distribution of the laser light in ydirection of the center axis of the beam spots after being combinedshown in FIG. 11(D). It is noted that the beam spot shown in FIG. 11(C)corresponds to the region satisfying the energy density that is 1/e² ofthe peak value of the energy density in FIG. 11(B). The energy densityis added in the portion in which each beam spot before being combined isoverlapped. For example, when the energy density E1 and the energydensity E2 of the overlapped beam as shown diagrammatically are added,the added value is almost equal to the peak value E3 of the energydensity of the beam. Thus the energy density is made flat between thecenters O of the respective ellipse.

It is ideal for the value added with E1 and E2 to be equal to E3. Infact, however, they are not always equal. It is possible for a designerto determine the margin of the gap between the value added with E1 andE2, and the value E3 appropriately.

As shown in FIG. 11(A), when the beam spot is employed singularly, it isdifficult to irradiate the semiconductor film or the whole part tobecome the island that contacts the flat portion of the insulating filmwith the laser light having homogeneous energy density since the beamspot has Gaussian energy distribution. FIG. 11(D) indicates, however,that it is possible to enhance the crystallinity of the semiconductorfilm effectively because the region having homogeneous energy density ismore enlarged by employing a plurality of laser light overlapped so asto compensate the part having low energy density each other thanemploying the laser light singularly not being overlapped with aplurality of laser light.

It is possible to perform the structure of this embodiment incombination with the embodiment 1.

1. A laser irradiation apparatus comprising: a first laser oscillator, asecond laser oscillator, a first optical system for converging firstlaser light oscillated from the first laser oscillator, a second opticalsystem for converging second laser light oscillated from the secondlaser oscillator, a chamber equipped with a window for transmitting thefirst laser light and the second laser light, means for supplying gasinto the chamber, means for evacuating the chamber, a stage for mountingan object to be processed thereon, and means for applying a magneticfield to the object, wherein the first laser light has a wavelength of aharmonic, and wherein the second laser light has a wavelength of afundamental wave.
 2. A laser irradiation apparatus according to claim 1,wherein the first and the second laser oscillators are continuous wavelaser oscillators.
 3. A laser irradiation apparatus according to claim1, wherein the first laser light has a wavelength of a second harmonic.4. A laser irradiation apparatus according to claim 1, wherein a beamspot of the first laser light and a beam spot of the second laser lightare overlapped.
 5. A laser irradiation apparatus comprising: a firstlaser oscillator, a second laser oscillator, a cylindrical lens and amirror for converging first laser light oscillated from the first laseroscillator, a cylindrical lens and a mirror for converging second laserlight oscillated from the second laser oscillator, a chamber equippedwith a window for transmitting the first laser light and the secondlaser light, a noble gas supplying system in the chamber, an evacuatingsystem in the chamber, a stage for mounting an object to be processedthereon, and a magnetic pole of a magnetic circuit for applying amagnetic field to the object, wherein the first laser light has awavelength of a harmonic, and wherein the second laser light has awavelength of a fundamental wave.
 6. A laser irradiation apparatusaccording to claim 5, wherein the first and the second laser oscillatorsare continuous wave laser oscillators.
 7. A laser irradiation apparatusaccording to claim 5, wherein the first laser light has a wavelength ofa second harmonic.
 8. A laser irradiation apparatus according to claim5, wherein a beam spot of the first laser light and a beam spot of thesecond laser light are overlapped.